It is well known that there are numerous production processes where the tiniest speck of debris may be damaging either in the end product or for an intermediate product. As such there are techniques known for the removal of particulate matter from such surfaces. Particles are rarely spherical with a single diameter, so the word diameter is widely used to describe particle size. In general, cleaning techniques include removal of particles with a tacky roll, tacky backings or tape, wet cleaning, and ultrasonic assisted air knife systems. Such production processes have also been conducted in “clean rooms”, which provide an environment relatively free of particulate contamination. However, such clean room facilities are expensive to operate and maintain.
There is a need for clean surfaces in high-volume roll-to-roll manufacturing using flexible webs having indefinite lengths, but that need has largely gone unfulfilled. These roll-to-roll production processes pose particularly problematic cleaning issues, because roll goods have relatively long lengths, which create huge surface areas that must be cleaned or kept cleaned. Such processed webs are typically wound into rolls that are stored and shipped in roll form and then unrolled when used or further processed. The rolling up, storage, shipping and unrolling of such cleaned webs creates opportunities for particulate contamination, especially when performed in relatively dirty locations. Even webs used as intermediate substrates that are, for example, coated, converted (e.g., slitting operations) or otherwise handled in continuous production processes can be exposed to particulate contamination over time, due to the nature of the processing equipment. In addition, such continuous web handling processes can be relatively large. Therefore, it can be expensive to perform such continuous web handling processes in a clean room environment.
Polymeric materials are often desired for use in making webs, for example, because of their flexibility and the variety of properties they can provide (e.g., optical, mechanical and thermal properties). However, polymeric web materials often have relatively softer surfaces, compared to surfaces that are typically cleaned (e.g., silicon wafers), which can further complicate particulate removal.